Electrophotographic photoreceptor having undercoat layer

Abstract

An electrophotographic photoreceptor, comprising an electroconductive substrate, an undercoat layer comprising a binder resin and metal oxide particles having a refractive index of at least 2.0 formed on the electroconductive substrate, and a photosensitive layer formed on the undercoat layer, wherein a ratio of a specular reflection of the undercoat layer calculated as a thickness of 2 μm to a light having a wavelength of 480 nm, to the specular reflection of the electroconductive substrate to a light having a wavelength of 480 nm, is at least 50%.

The invention claimed is: 
     
       1. An electrophotographic photoreceptor, comprising an electroconductive substrate, an undercoat layer comprising a binder resin and a metal oxide particle having a refractive index of at least 2.0 formed on the electroconductive substrate, and a photosensitive layer formed on the undercoat layer,
 wherein a ratio of a specular reflection of the undercoat layer calculated as a thickness of 2 μm to a light having a wavelength of 480 nm, to the specular reflection of the electroconductive substrate to a light having a wavelength of 480 nm, is at least 50%. 
 
     
     
       2. The electrophotographic photoreceptor according to  claim 1 , wherein the metal oxide particle comprises at least one selected from the group consisting of titanium oxide of rutile structure, lead titanate, potassium titanate, titanium oxide of anatase, zirconium oxide, zinc sulfide, and zinc oxide. 
     
     
       3. The electrophotographic photoreceptor according to  claim 1 , wherein the metal oxide particle has a refractive index of from 2.0 to 3.0. 
     
     
       4. The electrophotographic photoreceptor according to  claim 1 , wherein the binder resin is a phenoxy resin, an epoxy resin, polyvinylpyrrolidone, polyvinyl alcohol, casein, polyacrylic acid, celluloses, gelatin, starch, polyurethane, polyimide or polyamide. 
     
     
       5. The electrophotographic photoreceptor according to  claim 1 , wherein the metal oxide particle has a particle size of 1 nm or higher and less than 100 nm. 
     
     
       6. The electrophotographic photoreceptor according to  claim 5 , wherein the metal oxide particle has a particle size of from 1 nm to 50 nm. 
     
     
       7. The electrophotographic photoreceptor according to  claim 5 , wherein the metal oxide particle has a particle size of 5 nm or higher and less than 50 nm. 
     
     
       8. A method for producing an electrophotographic photoreceptor according to  claim 1 , comprising dispersing metal oxide particles in a coating fluid by a dispersing apparatus, where the dispersing apparatus comprises a dispersing medium having an average particle size of from 5 μm to 200 μm to form an undercoat layer, forming the undercoat layer comprising a binder resin and a metal oxide particle having a refractive index of at least 2.0 on an electroconductive substrate, and forming a photosensitive layer on the undercoat layer, wherein a ratio of a specular reflection of the undercoat layer calculated as a thickness of 2 μm to a light having a wavelength of 480 nm, to the specular reflection of the electroconductive substrate to a light having a wavelength of 480 nm, is at least 50%. 
     
     
       9. The method according  claim 8 , wherein the average particle size of the dispersing medium is in a range from 10 μm to 100 μm. 
     
     
       10. The method according  claim 8 , wherein a density of the dispersing medium is at least 5.5 g/cm 3 . 
     
     
       11. The method according  claim 8 , wherein a sphericalness of the dispersing medium is at most 1.08. 
     
     
       12. The electrophotographic photoreceptor according to  claim 1 , wherein the photoreceptor is obtained by a process comprising dispersing metal oxide particles in a coating fluid by a dispersing apparatus, where the dispersing apparatus comprises a dispersing medium having an average particle size of from 5 μm to 200 μm to form an undercoat layer, forming the undercoat layer comprising a binder resin and a metal oxide particle having a refractive index of at least 2.0 on an electroconductive substrate, and forming a photosensitive layer on the undercoat layer. 
     
     
       13. The electrophotographic photoreceptor according to  claim 12 , wherein secondary metal oxide particles dispersed in the coating fluid have a volume average particle size of at most 0.1 μm and a cumulative 90% particle size of from 0.10 μm to less than 0.20 μm. 
     
     
       14. The electrophotographic photoreceptor according to  claim 12 , wherein the secondary metal oxide particles dispersed in the coating fluid have a volume average particle size of at most 0.1 μm and a cumulative 90% particle size of from 0.10 μm to 0.16 μm. 
     
     
       15. The electrophotographic photoreceptor according to  claim 1 , an undercoat layer comprising a binder resin and a metal oxide particle having a refractive index in a range of from 2.0 to 3.0 formed on the electroconductive substrate, and a photosensitive layer formed on the undercoat layer,
 wherein the metal oxide particle is dispersion treated with a dispersion medium having an average particle diameter of 5 to 200 μm, and 
 wherein a ratio of a specular reflection of the undercoat layer calculated as a thickness of 2 μm to a light having a wavelength of 480 nm, to the specular reflection of the electroconductive substrate to a light having a wavelength of 480 nm, is at least 50%. 
 
     
     
       16. The electrophotographic photoreceptor according to  claim 1 , wherein an undercoat layer comprising a binder resin and a metal oxide particle having a refractive index in a range of from 2.0 to 3.0 formed on the electroconductive substrate, and a photosensitive layer formed on the undercoat layer,
 wherein one or more of the metal oxide particles are dispersion treated with a dispersion medium having an average particle diameter of 5 μm to 50 μm to obtain the undercoat layer, and 
 wherein a ratio of a specular reflection of the undercoat layer calculated as a thickness of 2 μm to a light having a wavelength of 480 nm, to the specular reflection of the electroconductive substrate to a light having a wavelength of 480 nm, is in a range of from 50% to 65.4%.